I was at Deep Creek yesterday with my wife and a friend, our two pooches too. We had a wonderful day dipping and enjoying the scenery. Such a great place to spend this time of year. We are all doing fine today, including the doggies. While I do not know what types of algae and other water plants are in Deep Creek, I am not noticing any varieties that I would consider different than past years. Its common in the late summer when the creek flow gets slow to see the proliferation of things that grow in the warmer water environment. There have been a number of ways suggested here in this thread for one if concerned especially about this issue to contact the appropriate authorities. While at Deep Creek naturally I tend to seek out for my swimming and dipping deeper cleaner areas of the creek. I have not seen any news this year, yet, about any dogs or people suffering from symptoms of toxic algae poisoning at Deep Creek. Of course I would like to hear about it if there had/has been any reports.